Chopblock

I think I've got the best one of them all! Next time you visit them, take him aside and say the following:

Well... "Dad" (chuckle here) I'm glad you asked because I've given this a lot of thought. As you know, your daughter deserves the best, and I'm going to be the best husband you and her could ever wish for.

(let that sink in, then continue)

We also understand your concerns, and want to reassure you that we have the utmost respect for the sacred union of matrimony, and all the traditions associated with it.

(again pause here as he starts to see where this is going then drop this bomb)

As you probably know, a "barely decent" wedding costs around $15,000.

(watch his face change)

Your daughter and I have already discussed what we feel is reasonable, and are not sure that we'll be able to get the wedding to be that cheap.

(you have to have done your homework here)

We've narrowed it down to 3 venues (pick whatever you want here) the cheapest of which is about $8,000. We've also discussed caterers (name a few, and say "A has the best reputation but B specializes in the type of cuisine we want") Continue listing some ridiculous wedding expenses. Then start on the honeymoon. If you need inspiration, get a copy of Marie Claire, or check bridal sites.

You can also imply something about how if the wedding isn't "good enough" that you are afraid she'll divorce you and move back in with her parents.

After you knock him around a bit, hopefully he'll interrupt and say something like "maybe you guys should wait a little bit and make sure you are ready"